January 15-16 Arctic Boundary Event

[TellicoWx]

NWS Nahville and Huntsville went with a WWA, NWS Birmingham a WSW

[TellicoWx]

Advisory map starting to fill in now

[TellicoWx]

Kinda surprised at NWS Birmingham WSW wording, says some spots up to 2". Haven't really seen that on any of the models.

[John1122]

MRX is always a holdout in these situations, OHX has 90 percent chance of snow across their CWA. JKL 80.  MRX 60. So MRX has 0 advisory products, not even a sps and 20-30 percent lower pops than their neighboring offices. 

[TellicoWx]

2 minutes ago, John1122 said:

MRX is always a holdout in these situations, OHX has 90 percent chance of snow across their CWA. JKL 80.  MRX 60. So MRX has 0 advisory products, not even a sps and 20-30 percent lower pops than their neighboring offices. 

Believe I saw earlier where someone said they are waiting until the afternoon 

[weathertree4u]

22 minutes ago, TellicoWx said:

NWS Nahville and Huntsville went with a WWA, NWS Birmingham a WSW

I believe, could be wrong, that the criteria for Winter Storm Watch is different for different parts of the country. For example, where I live north of Nashville, a Winter Storm Watch would have been issued if they expected greater than 4" but because less than that is expected, they went with a Winter Weather Advisory. For Birmingham, the Winter Storm Watch criteria may be 2" or less instead of 4" like it is around here.

[John1122]

6 minutes ago, TellicoWx said:

Believe I saw earlier where someone said they are waiting until the afternoon 

I'm sure they will issue products then, however it's not mentioned in their AFD which would normally be the case. Usually there's more coordination between WFO and this event is less than 24 hours away from beginning as the morning cycle unfolds. I see essentially no benefits to waiting.

[weathertree4u]

1 minute ago, John1122 said:

I'm sure they will issue products then, however it's not mentioned in their AFD which would normally be the case. Usually there's more coordination between WFO and this event is less than 24 hours away from beginning as the morning cycle unfolds. I see essentially no benefits to waiting.

My experience suggests that these arctic fronts are almost always over producers. I have seen them put down 4" - 5" powdery inches with no problem.

[TellicoWx]

4 minutes ago, weathertree4u said:

I believe, could be wrong, that the criteria for Winter Storm Watch is different for different parts of the country. For example, where I live north of Nashville, a Winter Storm Watch would have been issued if they expected greater than 4" but because less than that is expected, they went with a Winter Weather Advisory. For Birmingham, the Winter Storm Watch criteria may be 2" or less instead of 4" like it is around here.

Yeah their parameters are less, but even the RGEM didn't get to 2". Guess they would rather go that route and get people's attention, rather than have people caught off guard traffic wise.

[TellicoWx]

5 minutes ago, John1122 said:

I'm sure they will issue products then, however it's not mentioned in their AFD which would normally be the case. Usually there's more coordination between WFO and this event is less than 24 hours away from beginning as the morning cycle unfolds. I see essentially no benefits to waiting.

Yeah the AFD not mentioning it was a surprise, but like you said, they are notorious for lagging behind. Then you get to hear everyone complain that they didn't know lol.

[weathertree4u]

3 minutes ago, TellicoWx said:

Yeah their parameters are less, but even the RGEM didn't get to 2". Guess they would rather go that route and get people's attention, rather than have people caught off guard traffic wise.

You are correct. Though I work in Nashville, I am managed from an office in Birmingham. My manager was talking last week about how the local weather had totally missed the first one this year, I believe sometime in December they got dumped on with 5" or 6" I believe that was almost totally unpredicted.

[TellicoWx]

1 minute ago, weathertree4u said:

You are correct. Though I work in Nashville, I am managed from an office in Birmingham. My manager was talking last week about how the local weather had totally missed the first one this year, I believe sometime in December they got dumped on with 5" or 6" I believe that was almost totally unpredicted.

Yeah Birmingham turns into a mess with just a little snow on the roadways. Never forget when Spann missed his for cast and had to walk to work. It's also why I wish MRX would be a little more proactive instead of reactive.

[weathertree4u]

Just now, TellicoWx said:

Yeah Birmingham turns into a mess with just a little snow on the roadways. Never forget when Spann missed his for cast and had to walk to work. It's also why I wish MRX would be a little more proactive instead of reactive.

That is the way Nashville is or has been in the past. I believe recently they have gotten some younger blood in the office so they may be doing things different. If I were a forecaster, I would much rather take the heat of being wrong and letting people know what is possible then not saying anything because I do not think it is possible, only to have people's lives adversely affected. 

[Mrwolf1972]

Looking at the 500mb and 700mb upper air moisture  on the 6z nam and GFS the moisture flow looks good from the gulf into the valley  if I'm seeing it right if not somone tell me still learning this stuff takes till hr 48 on nam at 500mb and 700mb before it seems to cut off.

[Kasper]

3 minutes ago, Mrwolf1972 said:

Looking at the 500mb and 700mb upper air moisture  on the 6z nam and GFS the moisture flow looks good from the gulf into the valley  if I'm seeing it right if not somone tell me still learning this stuff takes till hr 48 on nam at 500mb and 700mb before it seems to cut off.

You are correct Wolf, looks juicy! 

[TellicoWx]

Good disco in HUN AFD:

not sold on the GFS
QPF, given that it does not appear to be resolving the synoptic
setup very well. Looking at forecast soundings, the GFS dries the
mid levels during the day, even while the upper levels and lower
levels are completely saturated. This drying is most likely due to
the GFS veering the winds to the west in this layer a bit early,
given the strengthening and eastward moving upper trough. Other
models, including the ECMWF and NAM, do not have as much drying as
they keep winds more backed to the southwest through the day. So with
this forecast, will lean more towards the ECMWF and NAM with greater
emphasis on the ECMWF given its consistency over the past few runs.
This would give the area between 0.04 and 0.08 inch of QPF, so not a
considerable amount more than the GFS. Given the snow ratios
mentioned above, this amount of QPF would equate to between 0.5 and 1
inch of snow across the region. Now, I`ve said this in the
discussion the last few mornings and I want to reiterate it. Just
because these amounts seem low does not mean they will not cause
significant impacts. It`s going to be very cold outside. In fact,
temperatures will likely be in the lower 20s. So the snow will stick
and it`s likely that it will stick to the roads. Given the warmer
conditions today, there`s a potential for the snow to initially melt
on contact and then refreeze in the colder temperatures. So don`t let
the low snow totals fool you. For these reasons, have decided to
issue a Winter Weather Advisory for the entire area on Tuesday,
beginning at 3 am in NW Alabama and at 6 am everywhere else.

[ShawnEastTN]

Been trying to remember the last time we had a scenario such as this with a front and think its been several years.  Though it seems I remember similar scenario and forecasts busted higher than, you can get intense rates at times in these where there is banding in the broader area of snow and that banding can bring amounts up quickly.  Glad to see the RGEM is on board at this point to, as that 24 hour window it generally seems to be very accurate form my experience watching it.  Expect MRX will issue WWA with afternoon products.

[ShawnEastTN]

Looking at the 6Z RGEM qpf think there will be a lot more folks who tick 3" than is generally being forecast.

[tnwxwatcher]

When is this generally expected to begin? Trying to start making contingency plans in case the schools close... do we think it will be tomorrow or Wednesday impacted? Just hoping they don't make a last second decision or when they are already there and dismiss early like in times past.

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[PowellVolz]

.

[ShawnEastTN]

5 minutes ago, tnwxwatcher said:

When is this generally expected to begin? Trying to start making contingency plans in case the schools close... do we think it will be tomorrow or Wednesday impacted? Just hoping they don't make a last second decision or when they are already there and dismiss early like in times past.

Sent from my SM-N900P using Tapatalk
 

Knox area seems window is somewhere around 12PM to 2PM start time tomorrow currently, that could change.  Wednesday morning would likely still be slick and wouldn't be surprised if schools are closed Wednesday at least some.  Tuesday it'll be interesting what schools decide to do, leave early or just close.

[tnwxwatcher]

Thanks for that information! Very helpful!

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[tnweathernut]

12z NAM continues to sharpen and deepen the incoming longwave trough through hour 18.

[Coach B]

6 minutes ago, ShawnEastTN said:

Knox area seems window is somewhere around 12PM to 2PM start time tomorrow currently, that could change.  Wednesday morning would likely still be slick and wouldn't be surprised if schools are closed Wednesday at least some.  Tuesday it'll be interesting what schools decide to do, leave early or just close.

I expect mass preemptive closings for tommorow in West and middle TN. If we get an inch or more most rural counties will be lucky to go back by Friday.

[Knoxtron]

Let's reel this puppy in! I am not sure if SREF's still provide good guidance or if we are nowcast time... but, I like the very slow uptick for Knoxvegas!

 

20180115/09 UTC SREF Runs

TYS - Avg 2", 8 runs with 2"+, 2 runs near 5"

CHA - Avg 1", 4 runs with 2-3"

TRI - Avg 1.7", 5 runs with 2"+, 2 runs 4-5"

[ShawnEastTN]

3 minutes ago, Knoxtron said:

Let's reel this puppy in! I am not sure if SREF's still provide good guidance or if we are nowcast time... but, I like the very slow uptick for Knoxvegas!

 

20180115/09 UTC SREF Runs

TYS - Avg 2", 8 runs with 2"+, 2 runs near 5"

CHA - Avg 1", 4 runs with 2-3"

TRI - Avg 1.7", 5 runs with 2"+, 2 runs 4-5"

I look at the plumes all the way until flakes are falling, and sometimes if it seems like it is out performing I will still take a peek at them to see if they ticked up during an event also.  It is nice to see them jump back up.

Also should add BNA mean is also at very close to 2", and so is MEM.  

[Bango]

12z name looks great for Tys, 

[bearman]

I talked to MRX and asked them why they have not issued any advisories or mentioned the system in there AFD. They said that they had not yet issued an advisory because model run-to-run consistency has been somewhat poor with this event leading to low confidence in the past couple of days. Fortunately the computer models are starting to come into better agreement on the timing of this system. So there will likely be an advisory issued later today.

[ShawnEastTN]

I wouldn't have expected them to issue before today just due to time frame still being about 24 hours out for a light event and Winter Weather Advisory product.  If this were not a light event and Watches were to be issued would have expected action sooner.

[Mrwolf1972]

12z nam 500mb and 700mb still look juicy and seems to be slowing down snow totals are saying 1-3 inches some places more.